W. Memeger et al., MACROCYCLIC ARAMIDS (2N-AZA[2N]PARACYCLOPHANE-2N-ONES) - NEW INTERMEDIATES FOR THE SYNTHESIS OF P-ARAMIDS, Macromolecules, 26(14), 1993, pp. 3476-3484
An easy route to a new class of 2n-aza[2n]paracyclophane-2n-ones, N-su
bstituted para-oriented cyclic aromatic amide (cycloaramid) oligomers,
is described. The bulky diamine N,N'-di-sec-butyl-p-phenylenediamine
is condensed with terephthaloyl chloride at elevated temperature in o-
dichlorobenzene to provide a high yield of N,N'-di-sec-butyl-p-phenyle
neterephthalamide cyclic oligomers (from dimer to tridecamer). (There
is evidence presented for the presence of cyclic unimer (a single repe
at unit), an amide analog of [2.2]paracyclophane, in the reaction prod
uct!) The cyclization is favored by the cis conformation of the N-subs
tituted amide bonds present in the growing chain. Ring-opening polymer
ization of these new cycloaramids to high molecular weight linear poly
mers can be effected in the melt phase with highly nucleophilic cataly
sts such as 1,3-dialkylimidazole-2-thiones, especially when an acid co
catalyst is employed. The N-substituted polymers yield crystalline fil
ms and fibers with an axial repeat length which can only be explained
by an unexpected trans conformation of the amide bonds. The facile syn
thesis of other macrocyclic amides by the steric control of macrocycli
zation by N-substitution of the amide bond is also described.